"No, it's not a Citation!!"
The X11
Updated 5/16/2000
The following is
information researched and compiled by Terry K, a fellow X-11 owner. I would
like to thank him for allowing me to use this information for my site to share
with all of you. I also have obtained some information and added it in the
appropriate areas. If you have any changes or corrections you would like to
see, please do not hesitate to email me
Well, it you want the real scoop, find the engineer. And that is what I have done. Through Scott Widmer, I was able to contact Jon Moss of the Chevrolet Specialty Vehicles who gave me the name of the original engineer for the X11, Mr. John Heinricy. John was more than willing to talk about the car that holds a special place in his heart. He was very open and took the time to answer all of my questions. I hope to add the transcripts of the conversation soon. There was just too much information to get all at once. He is happy to answer more questions in the future. As John said, "The X11 is not what you think it is..." It's more............
In 1979, General Motors introduced a completely new front-wheel drive chassis for the 1980 model year called the X-Body* series. All four product lines received a model with the Citation designation going to Chevrolet. (the Citation was originally going to be called the Condor.)
According to John, in 1979, GM wanted to race the Citation in the SSB/SCCA class and gave John, at that time a test engineer, the assignment to improve the suspension for the race car. He made the obvious changes, such as a stiffer suspension, better shocks, etc. He found that the cradle would actually warp under stress and that by adding diagonal braces at the rear cradle corners and braces from the cradle to steering rack, the handling went from acceptable to outstanding. If you look at 1981's, the corner braces are welded-in 1/2" rod. They were added back into the car for production after John took some executives out and showed them the importance of these braces. He took them for a ride with the braces and then ran back into the shop and ground them out for a comparison drive. The executives were convinced on the spot and agreed that the production cars must have the braces. In 1982, these were switched to bolt in braces. This is how it started.
The LH7 High Output "Z" engine was not even a pipe dream at this point. But John was racing the car and knew it needed more power. He knew the engine needed more air and started by stacking two stock air cleaners. Colder air would help even more. He cut the hood at the rear and ducted the air clear inlet to this hole. According to John, it makes far more difference that even I thought.
But there's more. John asked Tom Lange of the engine department to do some head work. The result was the HO heads with the larger valves and better port work. They knew that they could increase the compression and they did. Isky was asked to produce three different grand cams and the middle grind was used. The third grind was too radical. With some other changes, the High Output HO660 was born. Conservatively rated at 140HP and 145lbs of torque, this new engine was dropped into the 1980 X11 and began winning races. The 1980 production X11 received the tach (thus losing the clock), some decals, and the fake scoops on the side, but not the engine. Both the race car and the first production X11's were the notchback, not the hatchback. The 1980 production X11 had the suspension work and as a final touch the gearing was changed to allow 60MPH in second and a move up of first to help fill the stretch.
The executives were so happy with the racing success of the HO X11 that they decided to produce the car in small quantities (which was required by the rules.) They took the racing X11, designed new decals, added the Camaro cowl induction hood to accommodate the cold air intake and added the aluminum wheels. Other than these changes (and some emission controls), the racecar was going to be sold to the public. Unlike other knock-offs like the IROC Z28, where the car looks like the racecar, but is missing much of the mechanical changes, the X11 is the SSB/SCCA racecar. GM copied John's X11 down to the finest detail, added the extras and released it as the 1981 Citation X11.
The new engine was not available in the other X-Body cars until 1982. The engine went on to be the basis for the L44 (P) engine in the Fiero, the LB6 in the 1985 X-11 and Celebrity Eurosport, the LB8 in the Camaro, and up to through the hideous 3.4L DOHC.
Although the X-11 lasted only 6 years, it remains the unique muscle car that ushered in the front wheel drive era of power.
Z Engine (RPO LH7)
The Z engine had several differences from
its little brother, the X engine:
8.9:1 Compression Pistons (vs 8.5:1)
1.72" Intake and 1.42" Exhaust
valves (vs 1.60"/1.30")
.390"in./.410"ex. high lift
camshaft (vs .350"/.390")
Heavy duty oil pump
Dual intake-high volume air cleaner
Y-style exhaust system with 2-1/2"
pipes (dropped in 1982 for the wrap-around system, but the 2-1/2" in
exhaust pipes remained.)
Some
block improvements.
W Engine (RPO LB6)
In 1985, the X-11 received the MPFI version of the 2.8L V6. The main bearing sizes where increased from 63mm to 67mm mid-year. While the 67mm cranks are stronger, the 63mm crank has proven to be capable of standing up to just about anything you throw at it. The MPFI is not sequential but rather "batch mode." The induction control is via a Mass Air Flow sensor rather than the Fiero Speed Density using a MAP sensor. Why the difference? Both systems where first released in 1985 as a backup to each other should one fail federal certification. So it was quite possible that the Fiero could have been released with a MAFS or the X-11 could have used the MAP system had the other failed.
Transmissions
The X-11 came with either the THM125C 3-spd Hydromatic or the Muncie 4-spd. Due to the lower gearing, the automatic is quoted in some articles as being quicker, although I own both and the manual appears slightly faster. John says the manual is faster, period. Interestingly enough, my stock automatic will red-line in third gear (121MPH.) The Getrag licensed 5-spd was not available in the X-11, although it will fit with a few changes. The Isuzu 5-spd was deemed not beefy enough for the LH7 and was not used, although, it too will fit and for me has been fine. However, the MG2 Getrag has better gearing (actually a littler higher) and is a better choice. The THM440 4-spd automatic was available as an option in 1985. Interestingly, there was a special 3.56:1 gear ratio used for some small number of X-11 in the THM125C. The normal final drive was quoted as 3.33. But if you have one of the 3CD labeled trannies, it is 3.56 according to GM. The 3CD tranny does not appear in any of their service documents that I could find.
Suspension
The X-11 Z19 suspension is different that the standard F41. F41 means heavy duty and is listed as the X11 suspension. But if you order F41 in a stock Citation it is different from the F41 in the X11. Z19 was not available separately from the X-11 package. It sits roughly 2" lower than stock and 1" lower than F41. The ride is somewhat stiffer. Z19 consists of larger front and rear sway bars, higher rate coils, and better struts/shocks.
Added were braces to the cradle assembly to add stiffness, two from the cradle to steering rack and one across the rear cradle member connecting both sides of the exhaust pipe hump.
Finally, four aluminum 14X7" wheels with P215/60 tires rounded out the suspension. You may have more horsepower, but you can't out corner an X-11! If it over-steers, point the noise and pull the trigger. If it under-steers, stomp and pray. But whatever you do, don't let off the throttle!
Body
In addition to the Cowl Induction hood, a rear spoiler and decals topped of the look. With the lower suspension and hood, the look of the previous Citation was gone. Most people do not recognize the X-11 as having started as a Citation. In fact, the word Citation only appears in the door pillar flags (or citations!)
Interior
The interior was the optional Citation bucket seats available in several trims. However, the first noticeable change was the optional full gauge set including a 7000 RPM tach (vs the stock 6000 RPM tach). John says that he ran the LH7 at 6500-6800 all of the time and never have a problem other than a #4 rod bearing issue that was corrected with the larger oil pump. They never did find out why it was failing. A little closer look and you'll find the 80 PSI oil pressure gauge instead of the stock 60 PSI gauge. Some special merchandizing packages of the X-11 had the horrifying long speedometer with idiot lights! Few were built. Otherwise, they are complete X-11's.
In 1985, GM got smart and changed the dash to hold a "as god meant it to be" stereo radio in the horizontal position rather than the "no aftermarket stereo will fit" vertical position.
Next on the tour is the X-11 Sport Suspension trim above the glove box. It changed color over the years, but remained in all X-11's.
And topping it off is the official gold-circled silver and black X11 logo in the center of the steering wheel.
.
Cowl Induction
The functional cowl induction only operates when the engine is warm (TSTV on the intake open) and the throttle is open. The easiest way to test it is to snap the throttle open while feeling the damper door. It appears that there might have been a boot between the air-cleaner and the right angle duct. There was, but only the early 1981 Federal cars had it. It was removed after the car failed the California fuel evaporation tests. The cowl induction is a direct path to the carburator bowl. By removing the tight seal, the fuel vapors didn't flow directly out the hood. The seal was dropped for California and eventually for all cars. John recommends the seal be added back in. Otherwise, hot air from the engine can mix with the cold air from the outside. The cowl-induction was lost on the 1985 MPFI engines.
Vacuum Pump
Due to the low vacuum of the high-lift cam, the X-11 has a vacuum pump located in the driver side front wheel well to assist the brake booster at idle and those few times when you hold the throttle to the floor and jam on the brakes. With the engine off, pump the pedal four times and there should be a burrrrr for about 5 seconds from the front of the car.
Options
Many of the standard options were available in the X-11, although GM seemed to have mixed them up a lot without telling anyone. Ever seen the remote controlled rear swing-out windows?
4-Door?
This is one of those hallucinations. While in Placerville, I saw a 4-door X-11. I've never seen another except for a conversion by Jerry Roe.
What is the Z19?
More rumors. Z19 is the RPO code for the X11 Sport Package. Another rumor buster: The X11 was never called the Z19. Some people have made that claim, but John was clear on this point.
Why the X11 Designation?
The first X11's were the notchbacks or H11 body style. "X-car Body style 11". The hatchbacks were H08 body style. GM marketing took the X11 package, put it on a hatchback, and liked it so much it was produced. The public liked it too and the hatchback outsold the notchback. But for the tried and true, the X11 notchback IS the original X11. According to John, the notchback is stiffer, lighter and the preferred body.
X-11's & PRODUCTION NUMBERS BY YEAR
1980 X-11
This is nothing but a deckled
Citation with stiffer suspension.. One message stated they had a factory Z
engine in an 1980. Unless it was swapped or is an unknown end of year
conversion just prior to the 1981 release, this factory Z engine is extremely
unlikely.) None of the cars for this year came with the cowl-induction hood,
and the trim package was all that separated it from normal citations. It bore the X-11 symbol on the lower rear
quarter panels in front of a non-functioning intake vent. Both the notch and
hatches were available in this style.
1981 X-11
This was the first year for the true X-11. It used a Y-pipe exhaust system that collected below the engine. Gone was the Pulsar-Air system that was replaced with the Air-Injection-Air-Reaction System (AIR). This cleaned up the emission equipment clutter. The block used a two bolt alternator bracket. The EGR was controlled by a thermal switch in the intake manifold. An Early-Fuel-Evaporation (EFE) grid was added below the carburetor to improve cold drivability (and add air leaks.) The front motor mount was an L-bracket.
John says this is the car to own, especially in the notchback body. The power is higher and the original cradle design is far better at controlling power hop.
Total
Production: 11,631
1982 X-11
Some major changes occurred in 1982. First, the cradle was completely redesigned and was easier to separate for tranny removal. Second, the steering rack was moved to the cradle from the firewall to reduce vibration. The EGR was now solenoid controlled by the ECM. The exhaust system was changed to wrap around system (front-to-back.) This has been considered the move that dropped the horsepower slightly. 1981's are reported to have slightly better low-end torque. The wiring harness was cleaned up (but no longer had the connector at the firewall) and various fluid containers were moved. The lock-up torque converter was now available in the automatic. The front motor mount changed from the L-bracket to a U-bracket and the block has an additional hole drilled and tapped to accommodate it. However, the 1981 block had the boss and it could be drilled and tapped for use in later year cars. The fuel lines moved to the tranny side of the engine rather than the pulley side. The AIR system was basically the same, but the layout and routing was cleaned up.
Total
Production: 3,864
1983 X-11
The car remained essentially unchanged from the 1982 year. However, the distributor switched to the external coil version on the X-11, (which required adding a boss on the intake manifold for mounting) although I have received reports of the internal coil HEI being used. The EGR was changed to a pulse-width modulated system that improved its control. The EFE grid was now ECM controlled (vs thermal switch.)
Total
Production: 1934
1984 X-11
Further refinements to the emissions systems. The EGR solenoid was changed and moved. The ECM changed to a single board (use the 1894 Camaro Eprom!) To allow the ECM to control the A/C at wide open throttle (WOT), the EFE changed back to being switched by a thermal switch in the intake manifold and the EFE line was used to switch the A/C compressor.
Total
Production: 1458
1985 X-11
The 1985 was the first to receive the new LB6 (W) Multi Port Fuel Injection. This improved the low-end torque, increase the horsepower, and made for a more potent X-11. The system is a Mass-Air-Flow controlled system (the Fiero uses a MAP controlled system.) However, gone was the functional cowl induction (no more BWAAAAAA! at full throttle!) The fuel pump moved to the fuel tank. The THM440 4-spd automatic was now available. The dash was changed to a horizontal stereo radio. The Check Engine lamp driver module was removed (direct drive from the ECM). To accommodate the new air cleaner (move next to the evaporation canister), the coolant recover and washer tanks were moved to the driver's side. A relay/fuse assembly was mounted on the driver's side strut tower. The A/C and alternator swapped positions.
Total
Production: 1687
Which are the preferred
X-11's?
In order of preference (tranny is your choice):
Originally, I list the order as: "1985, 1981, 1984 or 1983, 1982. One
could argue the 1981 being number two. As far as power, they are slightly
better, but it is a model year short of receiving some of the refinements of
the later years. However, the ECM appears more tolerant of higher lift and
overlap cams." John says the 1981's are the best for power and will beat a
1985 MPFI. The 1981's also used a large mouth converter. The wrap-around
exhaust introduced in 1982 was a concession to the other X cars. (See Engine
Modifications.
Other X-11s
Citation XS
This was mid-way to the X-11. It lacked the cowl induction and used the F41 suspension, although the LH7 was available in 1982.
Turbo 660
This was a one time specialty car built by the Chevrolet Design Center in Michigan. GM used the LE2 and bolted on throttle body injection and a Borg-Warner/I.H.I RB6 turbocharger in a blow through system. The boost was run at 5PSI and alcohol injection helped minimize detonation. This engine produced 170hp. It lacked the cowl induction hood, but had flared fenders and Goodyear P235/60R14's on BBS wheels and a Canary yellow paint job. Contrary to popular beliefs, only one was produced. It was build by John Pierce at GM and was used as a show car and to scare people. It was later disassembled with the drive train going to a 1981 X11 owned by John. The body went somewhere unknown. John said the body is most likely gone.
ENGINE MODIFICATIONS (AT YOUR OWN RISK)
Emissions
At first I thought about just making the standard emission modification disclaimer. But here is my position. First, most of the after-market parts are 49-state legal and many have received the California EO approval. We can argue all day about your god-given-right to have power and pollute. Emission standards definitely affect the amount of power you can realize for a given modification. I do not condone the removal or modification of any emission related equipment. And I know you are now running to your engine to connected everything back up after that Mom and apple-pie declaration.
However, there is no reason why we can't build hi-power green engines that will pass emissions. With a little study, there is no reason to fear the emission equipment. I prefer to just go for the semi-annual check and pass without fear (CA.) I don't like how some of the laws are enforced, but I have discussed engine mods with CARB many times and found them to be down right reasonable as long as I was reasonable. I went through a long dissertation about swapping the 1985 MPFI to a 1983 block (only the crank journals are different and no mechanical fuel pump mount.) Their response was OK. If it makes sense, they will go for it. If you are an a**hole, they have a bigger stick to show you.
It is totally possible to build a 200hp CARB approved engine. But think about that, at this horsepower, the car becomes useful only for smashing ants at a stop light. But 200hp is nice at speed too.
Mods
First, whenever you are searching for mods on the Web, keep in mind that the Fiero L44 uses the same block (67mm). The cams, pistons, timing chains, and heads are the same. For the FI models, the intake, fuel rail and lower plenum are the same, but the top plenum is different. All of these parts will work in the LH7 or LB6. Searching for X-11 will return almost nothing. Except here, of course!
NOTE ABOUT ALUMINUM HEADS
The X-11 never had the aluminum heads. These
required dished pistons and had a compression ratio of 8.9:1. The aluminum
heads can not be used with the flat top pistons without lowering the piston
height. I have been told that, while the aluminum heads have improved flow,
they are not the preferred head for building hi-power engines. If you are
planning on building a 3.1L version, you will have to settle for 8.5:1
compression unless you mill the heads and intake manifold. So far, I have not
found 8.9:1 pistons for the 3.1L stroke with iron heads. Yes, custom pistons
can be easily made.
Power Chips
I know, what about more power? First, there few bolt on parts that will make any significant difference in the engine power. Even power chips (EPROMS) will make little difference in the overall power. GM actually did a good job of optimizing the chips for performance. However, if you call Hypertech, ADS, or Superchips, you get a "huh??" at the request for a chip for the X-11.
Well, there is a solution. It turns out the Camaro used the same engine, just mounted longitudinally and thus the same ECM. For the 1985 model year, the 2.8L (S) engine is the same, so just request a chip for this car (1226870 ECM.) In 1984, same thing (1226455 ECM.) In 1983, no chip, but all is not lost. The 1984 ECM will work in a 1983 system if the EFE relay is removed. The line from the ECM to relay is the A/C control line in 1984. Your 1983 A/C will be unaffected. This ECM will replace your 1226025 ECM. Ok, emissions. The EFE is used only for drivability on a cold engine. By increasing the fuel vaporization, the emissions are reduced during the time the EFE is on and the ECM goes closed loop. However, it is not listed as an emission component for testing. Making this change, however, may be considered a violation of emission laws. But the 1984 ECM has better EGR control so emissions may actually be better. So check first. The 1984 ECM also provides more data (for you Diacom fans.) For 1982, I have not reviewed this change. It may work, but you'll need to compare the wiring to the ECM. For 1981, it unlikely to work without just swapping to the 1983 or later emissions system completely. The 1981 carburator did not have the second EGR vacuum port on the secondary side needed for the 1983/1984 EGR PWM solenoid.
But don't expect anything serious from after-market "Power Chips". The most improvement is realized at full throttle. But this may only be 4-7% at best. Keep in mind that to get an EO approval, the emissions are tested without the mod and then with the mod. The mod must not increase the emissions over the un-modded values. So part throttle is basically unchanged. The torque converter lock-up point maybe moved.
Hook your EGR back up. The engine will ping otherwise and with the loud exhaust, you can't always hear it until the top of a piston opens up.
ADS Superchip (not Superchips!) 1984 ECM - 8405A Manual/8406A Automatic
1985 ECM - GM 1226870 - ADS 8507A Manual/8508A Automatic
1986 ECM - GM 1227302
Camshafts
There are several after market cams available. Be sure to ask if the cam is computer friendly. A high overlap cam will lower the vacuum so much the ECM will go nuts at idle and cause a rough idle (even though it may pass emissions.) The MPFI engines are more forgiving with the MAFS. The maximum lift should be limited to .560" to allow for piston clearance. Most camshaft lift "at the valve" is specified with 1.5:1 rockers. If you are using 1.6:1 the lift will need to be recalculated accordingly.
GM Stock X-11 Cam - .390" in. / .410" ex. GM P/N 14031378
GM (made by Crane) Hi-lift Cam - .420" in. / .442" ext. - GM P/N 12353919
Crane 260H10 - .440" in./.440" ext. Great power, but poor idle in carburated engines.
Camshaft Bearings
The small block V8 should be used to provide additional bearing surface. Two different bearings are used for the front and rear (#1 and #4) and the center two (#2 and #3). The oil hole should be located between 4 and 5 o'clock when viewed from the front of the block.
#1 and 4 GM P/N 474006
#2 and 3 GM P/N 474007
Rocker Arms
Several roller tipped or true roller rockers are available in 1.5:1 ratios. The Crane 1.5 true rollers are EO approved but the 1.6's aren't. The studs will need to be changed to 7/16" requiring the drilling and tapping the heads for the new studs. Any machine shop can do it. But true rollers really make a difference in hi-rpm performance.
Crane Hi-Intensity 1.5 Roller Rockers - 11756-12 ~$250
Crane Aluminum 1.5 Roller Rockers - 25750-12 ~$250
Competition Cams Magnum Roller Tipped Rockers 1.5:1 - 1413-12 ~$150
Competition Cams Magnum Roller Tipped Rockers 1.6:1 - 1414-12 ~$150
Note: 1.6 ration rockers typically not EO approved for the 2.8/3.1L engine.
Timing Chains
For any performance engine, a true double roller timing chain is a must. The Cloyes set is perfect for this engine.
Cloyes Roller Plus - 9-2137 $70
Cloyes True Roller - 9-3137 $85 (preferred) The stock chain dampener is not used.
Pistons
The HO V6 already uses 8.9:1 pistons, although GM (TRW) produced 12.5:1 pistons (these are not EO approved and just about useless on the street. They may have enough deck to cut them down to something reasonable.)
Crankshaft
The 2.8L 67mm journal block can accept the 3.1L crank. However, you will need to use flat-top pistons which limits the compression to 8.5. But the additional displacement offsets this reduction in compression. The 3.1L crank is internally balances, so you will need the matching flex-plate or flywheel. The 2.8L crank is externally balanced.
GM 3.1L Crankshaft (67mm journals - 1985 blocks and above only) - GM P/N 10078981
Note: This crank is intended for aluminum heads and dished
pistons. However, it can be used with 8.5:1 3.1L flat top pistons. IT CAN NOT
BE USED WITH 2.8L FLAT TOP OR 3.1L DISHED PISTONS WITH IRON HEADS . The correct
combination is 3.1L 8.5:1 flat top pistons and iron heads. I have not found
3.1L 8.9:1 flat top pistons yet. Second, it is internally balanced so it
requires the associated neutral balanced flywheel or flexplate.
Also, some early year 1985's have the 63mm journal blocks.
Oil Pump
The GM High-Volume High-Pressure Oil Pump is a must. Use the "blue-strip" spring to get 70PSI oil pressure at 2000rpm. These are cast iron pumps. The stock aluminum pump should be discarded as soon as possible! There are after market HV/HP pumps available that are fine.
GM Hi-Volume/Hi-Pressure Oil Pump - GM P/N 10051104 - ~$75
GM Hi-Pressure "Blue Stripe" Spring (70PSI) - 10044435 - ~$3.00
Heads
The Hi Output X-11 heads are just about everything you need. The first stock Citation heads gave the X engine about 105HP. Through substantial flow testing, the stock head gained an additional 17% more power to around 115HP. When used with the X-11 cam and pistons, this translated to 135HP. About the only thing to do is polish the first 1/2" into the ports and match the gaskets. Leave the intake vane alone. Milling the heads is not too wise due to the limited deck thickness. Failure of the head could occur. However, I know of several examples of milling up to .060". However, beyond .030", the intake must be milled to match the heads and it is likely the intake will sit on the block making the RTV sealing so thin it may fail. I am at about .040" on my heads and everything is fine. But I recommend any milling be limited to .030" or less. Better yet, limit milling only to correct flatness and use the stock .035" head gasket. Many after market head gaskets are as thick as .051" compressed!
Valve Covers
Tired of those stupid looking valve covers? Get the aluminum covers from the Fiero. For the carburated engines, the throttle return spring mount and throttle cable mount will need to be pulled off the old covers and mounted to the new covers. The lower part of the throttle lever will hit the covers, so grind it down or add a thick gasket under the carburator to lift up about .150". None of this is necessary on the 1985 MPFI engines. They just bolt on. Get the Fiero cover screws also, as they are different. The PCV and rear bank breather tube grommets are different too. This is easier than it sounds.
Rods
The 5.7L rods are the same length as the 2.8L. However, they must be narrowed to fit. But the 2.8L rods are totally acceptable for less than 7000rpm use.
Porting. Polishing and Balancing
For the cost, these are definitely worth it. The crank, rods, pistons, and flywheel should be balanced by a machine shop. The heads should have the intake ports polished and smoothed to remove any casting flash, but don't go in any farther than 1/2". And leave the "vane" (pointed tip in intake) alone. It improves the air flow 17%. Match the intake manifold gasket to the port openings.
Transmissions
I have used the Isuzu 5-spd in my manual X-11 without any problems. The installation is tricky only in that the cables need to be lengthened and front transsexual mount had to be made. But be aware that GM did not consider the Isuzu tranny to be beefy enough for the X-11. But they are a dime-a-dozen at the junk yards. In my case, I used took a 5-spd shift mechanism and switched the shift lever to the 5-spd mount and used the 4-spd cables. I had to make an adapter to move the cables forward at the tranny. The backup switch on the Isuzu is in the tranny rather than on the shifter, so the wires from the shifter need to be routed through the firewall to the tranny switch.
The preferred way is the Getrag (MG2) 5-spd. The gears are lower and more closely spaced. I am in the process of working out this swap. I know others that have done it and it should be no more difficult than the Isuzu swap. More to come.
The THM440 should go in with little difficulties. However, the Park/Neutral switch is on the tranny rather than the shifter, so it will need the wires routed through the firewall to the tranny.
Clutches
They're everywhere.
Suspension
In the 80's, several companies made suspension kits for the X-11. But I have not found any currently available. Custom springs are easy to have made, and Koni, KYB, and others make performance shocks. I consider the stock Z19 suspension to be fine unless you want to lower the car.
Check with:
AMP SPRING and SHAFT
P.O. Box 449, 24 Courthouse Drive
Loker Building, Leonardtown MD 20650-0449
Headers
Hooker at one time made headers for the X-11, PN 2146 or O-2146 1980-1981 (Injection tube holes). For the 1981, it is a little easier since the exhaust pipes dropped straight down from the manifolds. On the 1982-1984, it's a little trickier. Air injection and O2 sensor holes would be required. Also, some provision for the heat riser to the air cleaner would be required. 1985 owners would have it a little easier. A modified Fiero system could be used too.
MPFI Conversion
I completed the MPFI conversion of my 1983 manual transmission X-11. It was rather easy. The donor car was a 1985 Celebrity Eurosport. The total time required was about 15 hours. This is from removing the gas tank and installing the electric fuel pump to starting the car (which it did on the first snap of the key.) It turns out that GM made very few changes to the X-11 to put the MPFI on the engine. This is obvious from things like "Well, we don't need the Choke Heater, so we can power the fuel pump from that fuse." There were only about 6 wiring changes or additions that were needed. The starter wiring in the main power harness/connector had to move, the serial data line to the ALDL connector was added, the alternator field was powered through the choke heater so that was replaced with a 10 ohm resistor, and the electric fuel pump needed a wire from the connector under the rear molding to the ECM. All fuel lines were converted to hi-pressure lines with double clamps. The fuel filter was too difficult to mount back by the tankl, so I moved it to the engine compartment. The cat needed the air injection port sealed. Probably the biggest change was the Celebrity and Citation use different air cleaner intake nozzles. The Citation is shorter so I had to cut the Celebrity's down two inches. The wiper washer and coolant tanks were replaced with a dual tank from a 1981 Honda Prelude. Otherwise all connectors basically plugged right in. The 1983 manual X-11 didn’t use the VSS sender in the speedo so that was added.
The results were pretty dramatic. First, the engine was pretty pumped already. The MPFI smoothed out the idle nicely. There is still a significant lope, but the unsteadiness is gone. The carb engine is speed density and changes such as the cam play havoc with the ECM. The MPFI is Mass controlled which measures the air intake directly and is far more auto-adaptable. Speed density systems must calculate the air intake from the MAP and wild cams throw off the calibration.
The low-end torque went up the most. By 1500 rpm the torque is coming on strong and it pulls like crazy to 5000 RPM. It flattens a little to 6000 but I don't go beyond that. The mileage is about 25 on the road and 18-20 in town. I have yet to take out for a long drive to see what the extended mileage would be. However, if you keep putting your foot into it, it will drop the mileage into the 15-18 range real fast!
Anyone wanting more specific info should email me. The 3.8L TPI is next.
2.8L/3.1L/3.4L Bore vs Stroke
2.8L - 89mm Bore x 76mm Stroke
3.1L - 89mm bore x 84mm Stroke
3.4L - 92mm Bore x 84mm Stroke
3.1L
The 3.1L block is just the 1985 and later 67mm journal block. A 3.1L can be "made" for a carburated system or a "real" 3.1L could be swapped, but they are all FI, so several things need to change.
3.4L
The 2.8L/3.1L can not be bored for the 3.4L pistons although I have been told someone is doing it (I seriously doubt it's the 2.8/3.1 block.) GM told me the cylinder walls are too thin. However, GM does have a 3.4L upgrade that can be dropped into an X-11. And it's EO approved. The upgrade is intended for the longitudinal trucks and cars, but it should work since the transverse mounted engine uses a front block mount and tranny mounts. The block doesn't use the traditional side mounts. The starter holes would need to be drilled and tapped. Moving a transverse block to a longitudinal application is what gets tricky. But we don't care, do we!
One thing to remember is that a .030" (1mm) over bore 3.1L is about 3.2L. Pretty close to 3.4L.
3.8L Swap
More to come!
5.7L Swap
I am again rethinking this. If an external water pump is used, it just might fit. Since it will fit in the Fiero and the the Fiero has as little space from the pulleys to the frame as the X-11, it should go int. Phil keeps bugging me to look at it further. Mid-80 TPI's are getting cheaper all of the time. The adapter plate for the tranny is available, and now I am talking myself into it. It would be a dangerous X-11 especially to the driver.
SERVICE AND MAINTANACE
God, where is all of this oil coming from? Two places. The valve covers and distributor o-ring. The factory valve cover seal is RTV, the neoprene replacements solve this problem, but don't over torque the bolts or it will leak even worse. With 60PSI+ on the oil, the distributor o-ring needs to be replaced frequently, especially if you ever turn the distributor to time the engine. Get a hand full of them and replace the o-ring every 20,000 miles.
Synthetic Oils
The single biggest reason for synthetic oils is the cleanliness of the engine internals. I have obtained 280,000 miles+ on two X-11 engines. Was synthetic the reason? I don't know, but the engine was spotless when I tore them down. No sludge, no varnish. Also, at start-up there was never any lifter rattle from leakdown. Synthetic oils can be run longer to match the same equivalent cost of 3,000-5,000 mile oil changes. Just change the filter at 3,500 miles and run the synthetic 7,000 miles. I've run both Mobil 1 and Castrol SynTec and I don't see any difference.
Oil Filter
Switch to the AC PF52. It's longer and has increased filtering. An external mount should be considered if you are tired of oiling the cradle while removing the oil filter.
Air Filters
1985 X-11
Uses the AC 905C filter that is common to the Celebrity.
1981-1984 X-11
NAPA: 1781
AC Delco: AC781C
Wix: 6045
Fram: CA3705 (4" High)
Fram: CA3537 (2"
High)-can be stacked if desperate :)
Body Parts
The address for the warehouse which stores some X-11 parts is:
General Motors Service Parts
Operations (Plant76)
4400 West Mount Hope Road
Lansing Michigan 48917
Other Parts
I have seen rubber striping
for bumpers, NOS Decals, Cowl Induction hoods all go on sale on E-Bay. Try searching for X-11,
Chevrolet Citation, Chevy X-11, or any combination thereof in order to find
what you are looking for. You’d be surprised at all that goes on sale. Also,
you can find service manuals, magazine
specials on the X-11, keychains and more. Or once again, you can join the X-11
Club on Yahoo where there are about 45 of us who could help you find what you
need.
MUST HAVE BOOK!
GM Performance Parts P/N 12362500 $6.95 from
any GM Service Department
Chevy Power P/N 24502488 $19.95 from any GM
Service Department
How to Rebuilt Your GM V-6 60 Degree Engine
by Tom Currao ISBN 0-87938-841-2 $19.95 for most book stores. A must have!
X-Body Illustrated Parts Fiche (yes,
microfiche) from Bell and Howell.
This is the exploded parts diagrams and lists the dealer use. About $15.00.
Obviously, the GM Factory Service Manual from
Helm Incorporated in Highland
Park, Michigan, about $45.00.
Disclaimer: The information in this document is as accurate as possible at my level of intelligence. Finding facts about the X-11 is difficult at best. If I am wrong, correct me please! I take no responsibility for modifications suggested herein (or back there.)
* Technically, the 1975 Nova was the first X-Body car, but that's another story.